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Ultrafine Co₃O₄/SiO₂ nanocomposites were obtained via sol–gel (SG) method and related routes. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ adsorption–desorption techniques. The obtained phase, size of crystallites and specific surface area of the composites vary with the Co:SiO₂ weight ratio and preparation route. Humidity sensing properties measured by monitoring the DC conductivity for the obtained nanocomposites are reported. Conductivity changes amount to four orders of magnitudes were observed in response to 10–90% relative humidity change in the measuring chamber. Results indicate that humidity sensing properties depend on Co content and specific surface area of the composite.

This paper investigates the buckling behavior of graphene platelets (GPL) reinforced composite cylindrical shells with cutouts via finite element method (FEM) simulation. Young’s modulus of the composites is determined by the modified Halpin–Tsai micromechanics model while the mass density and Poisson’s ratio of the composites are approximated by the rule of mixture. Comprehensive parametric study is conducted to investigate the effects of the weight fraction and the shape of GPL fillers, the geometry of the shell and the position and orientation of the cutout on the buckling behaviors of the cylindrical structures. The results demonstrate that the addition of GPLs can significantly increase the load bearing capacity of the cylindrical shells. Larger sized GPLs with fewer single graphene layers are favorable reinforcing fillers in enhancing the buckling performances of the structures. The buckling load is sensitive to the location of the cutout with larger aspect ratio. Moreover, the orientation of the cutout is found to have significant effects on the buckling load when the orientation angle $\theta$ is falling within the ranges – $\pi$/2 $\le \theta \le$ – $\pi$/4 and $\pi$/4 $\le \theta \le \pi$/2.

The important enhancement in the structural, dielectric and optical properties of pure polymer and CdSe incorporated polyvinyl pyrrolidone has been reported in this paper. The surface morphology of CdSe/PVP nanocomposite film is studied by using scanning electron microscopy (SEM). The chemical composition of different elements has been reported using energy dispersive X-ray (EDX) spectrum. The structure of polymer nanocomposite is determined with the help of X-ray diffraction (XRD) spectrum and is observed to be hexagonal. Particle size, intercrystalline separation, interplanner spacing, lattice parameters, strain and dislocation factors are calculated using XRD results. Fourier transform infrared spectroscopy (FTIR) and Photoluminescence (PL) analysis have been studied in order to check the possible interaction between CdSe quantum dots and polyvinyl pyrrolidone (PVP) matrix. The ac conductivity of CdSe/PVP nanocomposite is found to be higher as compared to pure polymers. The highest value of conductivity observed at 60203 Hz and at 523 K is found to be $3.72\times 10^{-5}$Sm${}^{-1}$. Comparative study of dielectric constant, dielectric losses, dissipation factor, electric modulus and impedance has been performed. The semi-circles in impedance measurement for both materials show the bulk electrical properties that result in single relaxation process in CdSe/PVP nanocomposite.

The prime objective of this research work is to develop an efficient small scale-dependent computational framework incorporating microstructural tensors of dilatation gradient, rotation gradient, and deviatoric stretch gradient to analyze nonlinear lateral stability of cylindrical microshells. The numerical strategy is established based upon a mixed formation of the third-order shear deformable shell model and modified strain gradient continuum mechanics. The graphene nanoplatelet reinforcements are assumed to be randomly dispersed in a checkerboard scheme within the resin matrix. Accordingly, to extract the effective material properties, the Monte Carlo simulation together with a probabilistic technique are employed. The numerical solution for the microstructural-dependent nonlinear problem is carried out via the moving Kriging meshfree method having the capability to accommodate accurately the essential boundary conditions using proper moving Kriging shape function. It is represented that the role of the stiffening characters related to the effect of microstructural dilatation gradient, rotation gradient, and deviatoric stretch reduces continuously by going to deeper territory of the load-deflection stability path. Moreover, it is indicated that among various microstructural gradient tensors, the stiffening character of the rotation gradient is higher than deviatoric stretch gradient, and the stiffening character of the latter is more considerable than the dilatation gradient tensor.

The growth mechanism of WS₂ nanotubes in the large-scale fluidized-bed reactor is studied in greater detail. This study and careful parameterization of the conditions within the reactor lead to the synthesis of large amounts (50–100 g/batch) of pure nanotubes, which appear as a fluffy powder, and (400–500 g/batch) of nanotubes/nanoplatelets mixture (50:50), where nanotubes usually coming in bundles. The two products are obtained simultaneously in the same reaction but are collected in different zones of the reactor, in a reproducible fashion. The characterization of the nanotubes, which grow catalyst-free, by a number of analytical techniques is reported. The majority of the nanotubes range from 10 to 50 micron in length and 20–180 nm in diameter. The nanotubes reveal highly crystalline order, suggesting very good mechanical behavior with numerous applications.

Flexible dielectric composites with high permittivity have been extensively studied due to their potential applications in high-density energy capacitors. In this review, effects of interface characteristics on the dielectric properties in the polymer-based nanocomposites with high permittivity are analyzed. The polymer-based dielectric composites are classified into two types: dielectric–dielectric (DD, ceramic particle-polymer) composites and conductor–dielectric (CD, conductive particle-polymer) composites. It is highly desirable for the dielectric–dielectric composites to exhibit high permittivity at low content of ceramic particles, which requires a remarkable interface interaction existing in the composite. For conductor–dielectric composites, a high permittivity can be achieved in composite with a small amount of conductor particle, but associated with a high loss. In this case, the interface between conductor and polymer with a good insulating characteristic is very important. Different methods can be used to modify the surface of ceramic/conductor particles before these particles are dispersed into polymers. The experimental results are summarized on how to design and make the desirable interface, and recent achievements in the development of these nanocomposites are presented. The challenges facing the fundamental understanding on the role of interface in high-permittivity polymer nanocomposites should be paid a more attention.

Investigated herein are the small- and large-amplitude vibrations of a thermally postbuckled graphene-reinforced composite (GRC) laminated beam supported by an elastic foundation. The piecewise GRC layers are arranged in a functionally graded (FG) pattern along the thickness direction of the beam. The temperature-dependent material properties of functionally graded graphene-reinforced composites (FG-GRCs) are estimated through the extended Halpin–Tsai micromechanical model. The nonlinear governing differential equations are derived from the higher-order shear deformation beam theory and the von Kármán-type strain–displacement relationships. The thermal effect, the beam–foundation interaction and the initial deflection caused by thermal postbuckling are also included. A two-step perturbation approach is applied to determine the thermal postbuckling equilibrium paths as well as the nonlinear vibration solutions for the FG-GRC laminated beams. Results are presented to demonstrate the nonlinear vibration responses of thermally postbuckled FG-GRC laminated beams under a uniform temperature field. The effects of the FG reinforcement patterns and the foundation stiffness on the nonlinear vibration responses of FG-GRC laminated beams are examined and discussed.

Laminated beams made of nanocomposite materials have been used in many industrial sectors. This paper reports a study on the vibration behavior of laminated beams when experiencing the large amplitude vibration. The beams are made of perfectly bonded carbon nanotube-reinforced composite (CNTRC) layers. The novel constructions of CNTRC laminated beams with out-of-plane maximum negative Poisson’s ratio (NPR) are proposed. The volume fraction of CNT may change across the beam thickness which results in a piece-wise pattern. The material properties of the CNTRC layers are temperature-dependent and can be estimated by the extended rule of mixture model. The beams are considered to rest on a two-parameter elastic foundation and under differential thermal environmental conditions. The higher order shear deformation beam theory is applied to derive the motion equations of the nonlinear vibration of FG-CNTRC laminated beams. These equations include the influencing factors such as the geometrical nonlinearity in the von Kármán sense, the thermal effects and the beam–foundation interaction. The nonlinear vibration solutions can be obtained by employing a two-step perturbation approach. The nonlinear vibration characteristics of FG-CNTRC laminated beams under different sets of loading conditions and thermal environmental conditions are discussed in detail through a series of parametric studies. Numerical results show that the NPR has a significant effect on the large amplitude vibration characteristics of CNTRC laminated beams.

Silver nanoparticles (SNPs) have been successfully prepared using sol–gel method by annealing the sample at 550°C for 30 min. The SNPs were not confirmed by X-ray diffraction (XRD) analysis when the annealing temperature was considered at 450°C. They were also not confirmed without calcination of the sample. The physical mechanism of silver clusters formation in the densified silica matrix with respect to thermal treatment has been understood. The presence of silver metal in the silica matrix was confirmed by XRD analysis and TEM image of the samples. The average size of nanoparticles dispersed in silica matrix was determined as 10.2 nm by the XRD technique. The synthesized nanocomposites were also characterized by UV-Visible spectroscopy with a peak in the absorption spectra at around 375 nm. The distribution of particle size has been reported here in the range from 8 nm to 25 nm by TEM observations of the sample prepared at 550°C. The spherically smaller size (≈10 nm) SNPs have reported the surface plasmons resonance (SPR) peak less than or near to 400 nm due to blue-shifting and effect of local refractive index. Without annealing the silica samples the absorption spectra does not show any peak around 375 nm. The FTIR spectroscopy of the three types of samples prepared at different temperatures (room temperature, 450°C and 550°C) has also been reported. This spectra have provided the identification of different chemical groups in the prepared samples. It has been predicted that the size of SNPs by XRD, UV-Visible and TEM results have agreed well with each other. It may be concluded that formation of SNPs is a function of annealing temperature.

Conductive polyaniline/CeO₂ nanocomposite powders (PANI/CeO${}_2)$ were prepared by an in situ polymerization method. The effects of CeO₂ content on the microwave absorption properties of composites were investigated. The phase composition, morphological characteristics, electromagnetic parameters and microwave absorption properties of the composites were characterized through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and vector network analysis. Results show that CeO₂ nanorods are coated with PANI to form a well-defined hierarchical structure. CeO₂ is well-incorporated into the PANI matrix. CeO₂/PANI exhibits excellent microwave absorption properties at 2–18GHz. As the CeO₂ content increases to 30wt.%, an optimal reflection loss (RL) of $-$40dB (99.99% of electromagnetic wave absorption) is observed at 8.8GHz with a thickness of 3.0mm. The frequency bandwidth corresponding to 90% of electromagnetic wave absorption crosses the X-band. Therefore, PANI/CeO₂ can be used as an advantageous candidate for a new type of microwave absorptive material.

Nanoparticles succeeded to enhance the dielectric properties of industrial insulation but the presence of voids inside the power cable insulation still leads to formation high electrical stress inside power cable insulation material and collapse. In this paper, the dielectric strength of new design nanocomposites has been deduced as experimental work done to clarify the benefit of filling nanoparticles with different patterns inside dielectrics. Also, it has been studied the effect of electrical stress distribution in presence of air, water and copper impurities with different shapes (cylinder, sphere and ellipse) inside insulation of single core. In simulation model, it has been used finite element method (FEM) for estimating the electrostatic field distribution in power cable insulation. It has been applied new strategies of nanotechnology techniques for designing innovative polyvinyl chloride insulation materials by using nanocomposites and multi-nanocomposites. Finally, this research succeeded to remedy different partial discharges (PD) patterns according to using certain types and concentrations of nanoparticles.

The structural, morphology, and optical properties of a new hybrid structure prepared from CuO nanoparticles embedded in a Fe₂O₃–PVA composite matrix were investigated in this work. Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), absorption and transmission spectra, and Fourier transform infrared spectroscopy (FT-IR) were all used to analyze the prepared materials. Crystallography information revealed the presence of CuO that did not affect the crystal structure of PVA–Fe₂O₃. The prepared composites revealed strong absorption in the range of 440–570 nm. It was observed that the highest absorption of these composites gradually shifted to the shorter wavelength region with the presence of CuO. PVA–Fe₂O₃ is highly transparent, with a transmittance of around 85% in the range of 600–800 nm. After the addition of 5% by weight of CuO nanoparticles, the transmittance of the nanocomposite drops to 75% in the same range of wavelength. The prepared materials were used as anti-cancer cells, and they showed high efficacy to kill tumor cells, especially PVA–Fe₂O₃–CuO at concentration 0.5 $\mu$g/mL.

In this work, the free vibration of a spinning polymer/fiber/GNP laminated truncated conical shell with non-uniform thickness is analyzed. The conical shell is made of a polymeric matrix reinforced with aligned fibers and uniformly distributed graphene nanoplatelets (GNPs). The elastic constants and density of the nanocomposite are estimated utilizing micromechanical equations, the Halpin–Tsai model, and the rule of mixture. The conical shell is modeled via the first-order shear deformation theory (FSDT) incorporating relative, centrifugal, and Coriolis accelerations alongside the initial hoop tension. Hamilton’s principle is hired to derive the governing equations and boundary conditions. The differential quadrature method (DQM) is hired to provide a numerical solution in the meridional direction alongside an analytical solution presented in the circumferential direction. The effects of several parameters on the natural frequencies and critical rotational speeds are inspected including thickness variation parameters, mass fractions of the fibers and the GNPs, stacking sequence, and boundary conditions. It is discovered that to achieve higher natural frequencies and critical rotational speeds, it is better to increase the mass fractions of the GNPs and fibers and align the fibers in parallel with the meridional direction.

Curved nanobeams are one of the essential components in manufacturing nano-electromechanical systems needing nonlinear stability design. In the current investigation, the nonlinear buckling characteristics of functionally graded porous reinforced curved (FGPRC) nanobeams having different degrees of curvature are analyzed by counting the higher-order gradients of the classical strain tensor as well as nonlocal-type interatomic interactions. In this regard, two independent length-scale constants within the framework of the nonlocal strain gradient theory (NSGT) of continuum elasticity are taken into account. Via employing the promising low computational cost and geometrically adaptable method of isogeometric collocation, various branches of NSGT-based equilibrium graphs of FGPRC nanobeams are plotted relevant to each considered degree of curvature. It is extrapolated that the quantity of graphene platelet (GPL) weight fraction has a negligible influence on the significance of nonlocal-type of interatomic size dependency as well as the strain gradient kind of small-scale effect in the value of the maximum deflections or lateral loads at the detected limit points, especially attributed to a higher degree of curvature. Besides, it can be remarked that, in the FGPRC nanobeam owning a small degree of curvature, lessening the quantity of porosity index results in an increment in the significance of the nonlocal-type of interatomic size dependency as well as the strain gradient kind of small-scale effect on the maximum deflection at both upper and lower limit points. However, in the FGPRC nanobeams owning medium and large degrees of curvature, it gets lesser at the upper limit point, but becomes higher at the lower limit one.

The aim of this work is to synthesize nickel sulfide–graphene (NiS/G) nanocomposites with different compositions and to analyze the structural and electrochemical capacity and compatibility for their application as supercapacitor material with enhanced charge storage capacity and reduced impedance. NiS nanoparticles (NPs) loaded on graphene were synthesized at various concentrations of graphene by a simple hydrothermal route from nickel sulphate and graphene oxide as precursors in the presence of PVP as surfactant and thioacetamide (TAA) as sulfur source. The composites structural, morphological and physical properties were analyzed by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier Transform-infrared (FT-IR) analysis. SEM measurements showed the presence of surface attachment of the NiS NPs onto the graphene sheets. To assess the properties of the nanocomposites for their applicability in supercapacitors, electrochemical analysis was carried out in 6M KOH electrolyte. Three different samples with different graphene contents — GNiS-10 with 10 wt.%, GNiS-20 with 20 wt.% and GNiS-40 with 40 wt.% were prepared. The specific capacitances obtained for the nanocomposites were calculated to be 84.33F/g, 129.66F/g, 187.53F/g at 10mV/s scan rate, respectively. The EIS data showed that the loading of NiS NPs on graphene caused the reduction in impedance at high frequency and has a long cycle life (over 1000 cycles).

This paper reports the photoconductive and antimicrobial properties of SnS₂–CdO and SnS₂-NiO nanocomposites green synthesized using Psidium guajava leaf extract. X-ray diffraction studies reveal that the SnS₂–CdO nanocomposite exhibits hexagonal SnS₂ and cubic CdO diffraction peaks; whereas the SnS₂–NiO nanocomposite exhibits hexagonal SnS₂ and cubic NiO diffraction peaks. SEM image of the bio-synthesized SnS₂–CdO nanocomposite confirmed nanoneedles with grains being well distributed. Regular shaped grains with decreased sizes were observed for the SnS₂–NiO nanocomposite. Nanosized grains were observed from the TEM images. The existence of elements Sn, S, Cd, O in SnS₂–CdO nanocomposite; Sn, S, Ni, O in SnS₂–NiO nanocomposite was confirmed from the EDX and XPS spectra. Increased photosensitivity value was realized for the SnS₂–CdO nanocomposite. Both the composites showed good fungal inhibition property against Aspergillus terreus fungi not only by the physical, chemical and biological processes but also owing to phyto-constituents in the leaf extract.

Hierarchical TiO₂/carbon nanocomposites were synthesized by oxidation of two-dimensional (2D) Ti₃C₂ nanosheets at different temperatures. Crystal structures and morphologies of the obtained samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectroscopy. The results show that 2D Ti₃C₂ nanosheets are partially oxidized to form a novel hierarchical nanostructure which is composed of carbon nanosheets and TiO₂ nanoparticles. With the calcination temperature increasing, the crystal structure of TiO₂ nanoparticles changes from anatase to rutile and the hierarchical structure was gradually destroyed. The photodegradation results reveal that the samples obtained at 200°C and 285°C show much better photocatalytic properties than P25. And meanwhile the photocatalytic property will become worse with the increase in calcinations temperature.

Cross-linked polyvinyl alcohol (PVA) graphene oxide (GO) nanocomposites were prepared by simple solution-mixing route and characterized by Raman, UV–visible and fourier transform infrared (FT-IR) spectroscopy analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD pattern and SEM analysis showed significant changes in the nanocomposite structures, and the FT-IR spectroscopy results confirmed the chemical interaction between the GO filler and the PVA matrix. After these morphological characterizations, PVA-GO-based diodes were fabricated and their electrical properties were characterized using current–voltage (I–V) and impedance-voltage-frequency (Z-V-f) measurements at room temperature. Semilogarithmic I–V characteristics of diode showed a good rectifier behavior. The values of C and G/$\omega$ increased with decreasing frequency due to the surface/interface states (N${}_{\mathrm{\text{ss}}}$) which depend on the relaxation time and the frequency of the signal. The voltage, dependent profiles of N${}_{\mathrm{\text{ss}}}$ and series resistance (R${}_{\mathrm{\text{s}}}$) were obtained from the methods of high-low frequency capacitance and Nicollian and Brews, respectively. The obtained values of N${}_{\mathrm{\text{ss}}}$ and R${}_{\mathrm{\text{s}}}$ were attributed to the use of cross-linked PVA-GO interlayer at the Au/n-Si interface.

Polyaniline (PANI) is recognized as one of the most important conducting polymers due to its high conductivity and good stability. In this paper, polyaniline/silver (PANI/Ag) nanocomposites were synthesized by in-situ polymerization of aniline using ammonium peroxydisulphate (APS) as oxidizing agent with varying concentration of Ag nanoparticles colloids (0 ml, 25 ml and 50 ml). Silver nanoparticles were synthesized separately in colloidal form from silver nitrate (Ag₂NO₃) with the help of reducing agent sodium borohydride (NaBH₄). The PANI/Ag nanocomposites were characterized by XRD, SEM, AFM, UV-visible, temperature dependent resistivity and dielectric measurements. All samples show a single phase nature of the nanoparticles. The electrical resistivity as function of temperature was measured in the temperature range 298–383 K, which indicates a semiconducting to metallic transition at 373 K and 368 K for 25 ml and 50 ml silver colloid samples, respectively.

This work examines the effects of WC nanoparticles on nanohardness, elastic modulus and scratch-induced wear behavior of Mg-based metal matrix nanocomposites. Ultrasonic vibrator-equipped stir casting furnace is used to fabricate Mg–WC nanocomposites. Scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX) and X-ray diffraction (XRD) are employed to conduct the characterizations of base alloy and Mg–WC nanocomposites. Vickers microhardness tester is used to obtain the microhardness values of the fabricated materials. Nanoindentation tests are performed to find the effect of wt.% of WC on the mechanical properties, i.e., nanohardness and elastic modulus. Nanohardness and elastic modulus present nearly 122% and 169.37% increments, respectively, compared to the base alloy when only 2wt.% of WC is present as reinforcement. Scratch tests are performed to find the effects of wt.% of WC and applied load on the scratch-induced wear and coefficient of friction (CoF) of the base alloy and Mg–WC nanocomposites. Wear volume also decreases continuously with increase in the weight percentage of WC in magnesium alloy. The COFs of nanocomposites are almost constant but they are inclined to increase with the increase in wt.% of WC. Finally, SEM micrographs of scratch grooves are analyzed to find the wear mechanisms. Abrasive wear mechanism is found to be the dominant one regarding the scratch of Mg–WC nanocomposites.